Drive unit comprising a retarder

ABSTRACT

The invention relates to a drive unit of a motor vehicle provided with a cooling circuit, said drive unit comprising a hydrodynamic retarder having a rotor vane wheel and a stator vane wheel, the hydrodynamic retarder being arranged in the vehicle cooling circuit and the working medium of the retarder being the vehicle cooling medium. The inventive drive unit is characterized in that means for removing a pre-determined quantity of working medium from the cooling circuit during the changeover from braking mode to non-braking mode, and for supplying a pre-determined quantity of working medium into the cooling circuit during the changeover from non-braking mode to braking mode, are connected to the cooling circuit.

The invention involves a drive unit, in particular, including thecharacteristics described in the preamble included of claim 1.

A retarder for the purpose of decreasing speed or rotational frequencyis often integrated into vehicle drive systems or stationary systems.When used in motor vehicles or in systems with highly changingoperations due to filling and draining the blading working cycle, theretarder is activated and de-activated by means of an operating fluid.

The stationary or mobile units, as, for instance, motor vehicles, intowhich the above-mentioned drive units are integrated, usually haveadditional aggregates that require cooling. This includes, for instance,motors, brakes, clutches, and gearboxes.

These additional aggregates could also have a cooling circuit in orderto cool down the working medium. p A large number of patents introducedRetarders to us in which the working medium of the retarder is thecooling medium of the vehicle.

In this regard, reference could be made to

-   EP 0 716 996 A1-   WO 98/15725-   EP 0 885 351 B1-   EP 0 932 539 B1

The disclosure content of these patents is completely included in theapplication at hand.

In order to keep the power loss of these retarders in non-braking modeat a low level, most of the working medium is drained from the workspaceof the retarder in non-braking mode. During the changeover [fromnon-braking mode] to braking mode, in turn, the retarder is quicklyfilled with working medium. The disadvantage of this process is the factthat during the changeover from braking mode to non-braking mode, andfrom non-braking mode to braking mode, high-pressure impulses take placein the system which put stress on the individual component parts.

The invention has the objective to present a drive unit comprising aretarder that could be filled and drained, in particular a waterretarder, specifically a secondary water retarder which does not haveany pressure impulses during the changeover from braking mode tonon-braking mode, or vice versa, or such pressure impulses are at leastto a large extent decreased.

This objective is reached through a drive unit which includes thecharacteristics described in claim 1. The dependent claims describeparticularly practical improvements of the invention.

According to a first embodiment of the invention, a connected dampercylinder is attached to the cooling circuit which removes apre-determined quantity of working medium from the cooling circuitduring the changeover from braking mode to non-braking mode, and whichsupplies a pre-determined working medium into the cooling circuit duringthe changeover from non-braking mode to braking mode. For this purpose,the supplied quantity of working medium, in particular, corresponds tothe previously removed quantity of working medium.

According to a further development, the damper cylinder is connected attwo places to the cooling circuit so that it works automatically.

According to an additional or alternative embodiment, a bypass sectionwith a connected bypass valve has been provided in the cooling circuitwhich opens during the changeover from braking mode to non-braking modeand gives way to an additional line section which, at least temporarily,accepts a pre-determined quantity of working medium.

Subsequently, the invention shall be described in more detail by meansof figures of various embodiments.

It is shown

FIG. 1 a first embodiment of the invention;

FIGS. 2 and 3 a second embodiment of the invention;

FIG. 4 a third embodiment of the invention.

In FIG. 1, a secondary retarder (100) is shown which is operated withthe cooling medium of the vehicle. The retarder shown in FIG. 1 ismarked by a low level of power loss.

According to a first method, the rotor vane wheel (11) is positioned onthe rotor shaft (110) axially relocatable so that the rotor (11) couldbe brought into working position close to the stator (12) or intoresting position with considerable distance to the stator (12) duringthe non-braking mode. In FIG. 1, the retarder is shown in restingposition. With regard to the relocatibility of the rotor, reference ismade to WO 98/35171.

The retarder shown in FIG. 1 comprises a rotor (11) which is supported,torque proof and in an overhung position, on a spinning shaft (110), theso-called retarder shaft which, in turn, is imbedded, for instance, in agearbox. The shaft (110) with the bearings (22 and 23) is powered via apinion (21) by the drive shaft of a gearbox, which is not displayed inthe figure. By means of a helical tooth system, which is not displayed,the rotor (11) could be laterally moved on the shaft (110) so that thedistance between rotor and stator could be adjusted. In non-brakingmode, the spring (18) could adjust the rotor (11) into the displayedlow-loss position, resulting in a maximum gap between rotor and stator(12). The retarder has a retarder housing (130) with an internal space(16). This internal space (16) is filled with cooling medium and acts ascooling jacket. The space between rotor (11) and stator (12) is referredto as workspace (140) and is filled with working medium. Thehydrodynamic retarder is integrated into the cooling circuit (120) ofthe motor vehicle. Consequently, in the displayed embodiment of theretarder, the working medium of the retarder is also the cooling mediumof the motor vehicle. In order to keep the idling losses at a minimum,the retarder has to be drained in non-braking mode. This draining wouldalso include an emptying to a pre-determined remaining quantity ofworking medium, which practically would result in minimal power loss.

This draining process, which is mainly activated by the pumping actionof the rotor (11), is basically controlled by the control valve (17).

In order to adjust the pressure impulse, which enters the coolingcircuit (120) because of the fact that the quantity of working mediumcontained in the retarder during braking mode is drained relativelyquickly into the remaining cooling circuit (120), a damper cylinder (30)has been provided. During the changeover from braking mode tonon-braking mode, this damper cylinder (30) accepts a pre-determinedquantity of working medium. Later, during the changeover fromnon-braking mode to braking mode, the pressure impulse, which occursbecause of the fact that during the filling period the retarder removesrelatively quickly a certain quantity of working medium from theremaining cooling circuit (120), is once again adjusted. It is adjustedby the fact that the quantity of working medium contained in the dampercylinder (30) is re-circulated into the cooling circuit (120).

The circuit of the damper cylinder, which has a piston (30.1) and acompression spring (30.2), is being adjusted via the pressure in theline (38). The pressure in the line (38), in turn, is being adjusted viathe valve (31). This shows that the line (38) has a current-conductingconnection to the side of the cylinder (30) which is opposite to theside of the cylinder (30) having the compression spring. As a result,the compression spring (30.2) presses the piston against the pressure inthe line (38).

The check valves (34 and 35) in the lines (32 and 33) accomplish that,during the changeover from braking mode to non-braking mode, the workingmedium is basically removed from the workspace (140) of the retarder orthe conduction branch behind the workspace. During the changeover fromnon-braking mode to braking mode, the working medium is re-circulated tothe line (19) via the line (33).

In the embodiment shown in FIG. 1, the hydrodynamic retarder comprisesthree different seals. One of the seals is an axial face seal withabsolute impermeability toward the outside—toward the atmosphere—and isconstantly washed around in cooling fluid (14). Another seal (15) has tofulfill two sealing functions. During non-braking mode, the coolingfluid, which could constantly flow through the inside space (16) of theretarder housing via the line (19), is absolutely sealed in thedirection of the rotor and stator; that is, in non-braking mode, theseal (15) accepts the sealing function. During braking mode, thesplit-ring seal (15.1) acts as non-contact labyrinth seal, and thecooling fluid flows through the seal (15) which, in this case, is notperforming any sealing function. In this way, it is guaranteed that,during brake mode, the seal (14) is lowered to the pressure level of theclosed cooling system.

The interior (16) is shaped in a way that it functions as heatdispensing cooling jacket of the retarder in which the cooler medium issupplied via the line (19) and drained via the line (20).

FIGS. 2 and 3 show alternative embodiments of the invention. These arecharacterized by the fact that the supply and removal of the workingmedium by means of the damper cylinder (30) takes place automatically,that is, exclusively dependent on pressures in the cooling circuit. Viathe line (42), the damper cylinder transporting the working medium isconnected to a place of high pressure behind the retarder (100) and thecontrol valve (17) which controls the draining of the retarder (100)and, via the line (41), it is connected to a place of low pressure infront of the retarder (100) behind the reversing valve (13) transportingthe pressure. During the changeover from braking mode to non-brakingmode, the reversing valve (13) changes the working medium flow in such away that the retarder (100) is no longer supplied with working mediumvia the line (43), but the entire working medium is directed via thebypass (66) around the conduction branch of the cooling circuit with theretarder (100). Accordingly, the pressure in the line (43) and,consequently, also in the line (41) connecting to the pressuredecreases. The piston (30.1) of the damper cylinder (30) is pressedagainst the thrust force of the compression spring (30.2) and receivesvia the line (42) working medium from the cooling circuit (120).Consequently, the portion of working medium, which is removed from theretarder (100) during the process of draining, is “collected” in thedamper cylinder (30), and the particular pressure impulse caused by thedraining of the retarder is decreased.

During the subsequent changeover from non-braking mode to braking mode,the reversing valve switches the working medium flow once again to theline (43) in the direction of the retarder (100). As a result, thepressure in the line (43) and, consequently, also in the pressure line(41) connecting to the damper cylinder (30) increases. This increasingpressure together with the thrust force of the spring (30.2) presses thepiston (30.1) of the damper cylinder (30) opposite to the staticpressure from the line (42) and, consequently, pushes the quantity ofworking medium contained in the damper cylinder (30) back into thecooling circuit (120). As a result, at least partially, the pressureloss in the cooling circuit (120), which results from the process offilling the retarder (100), is adjusted.

The embodiment according to FIG. 3 basically corresponds to theembodiment according to FIG. 2. Corresponding component parts have thesame reference numbers as in FIG. 2. One difference is the arrangementof the retarder circuit in the cooling circuit (120) of the vehicle. InFIG. 3, when the retarder is being connected, the branch of the coolingcircuit with the retarder (100) is positioned between the cooling pump(2) and the motor (1). In FIG. 2, on the other hand, this circuit branchin the cooling circuit (120) was positioned behind the motor (1). As inthe embodiment according to FIG. 2, a shutoff valve (62) is beingdesigned which could be switched to opening position, as well as apressure relief line (64) which is connected to the compensatingreservoir (6). The pressure shutoff valve (62) is located in thepressure relief line (64). In case of high-pressure peaks, such asimpulse impacts during the process of draining the retarder, it will beopened. Because of this additional measure, pressure peaks occurring inthe cooling circuit during retarder operation or during the changeoverfrom braking mode to non-braking mode could be further reduced. Thepressure relief line (64) is directly connected to the compensatingreservoir (6).

FIG. 4 shows a further development of the invention. The displayedwiring diagram shows measures that were taken in order to prevent to alarge extent the occurrence of a pressure impulse in the system, inparticular, in the line (51) during the changeover of the retarder frombraking mode to non-braking mode. In addition, measures are displayedwhich could be performed additionally or alternatively in order toprevent the occurrence of a pressure impulse or spontaneous pressureloss during the changeover from non-braking mode to braking mode.

The measures mentioned first—prevention of disconnection impact—arebasically epitomized by means of the pressure-connected valve (62) withthe connected lines (64 and 65). With its end facing away from the valve(62), the line (64) is located in a high-pressure area of the coolingcircuit. This could, for instance, be in the area of the working mediumoutlet of the retarder or at a draining channel, which is designed inthe retarder housing. There could be, for instance, a pressure of 11 barat the beginning of the non-braking mode. A further practicalpossibility of connection could result from the position between thedisplayed check valve and the adjustable choke of the control valve(17). There could be, for instance, a pressure of 30 bar.

With its end facing away from the valve (62), the line (64) is connectedin a low-pressure area of the cooling circuit. Practically, there is amaximum pressure of 2 bar. The connection could, for instance, bearranged in the area of the inflow of the retarder (100), in particular,at a filling channel, which is arranged in the retarder.

Profitably, the control of the valve (62) takes place with the samecontrol impulse with which also the valve (13) is controlled. Inparticular, both valves are being connected by means of a pressureimpulse (p-connected). During the changeover from braking mode tonon-braking mode, the valve (62) is changed from a closed position to anopen position. This will result in a short circuit flow via the retarder(100), that is, working medium, in this case, the cooling medium of thevehicle flows from the high pressure area mentioned above via the lines(64 and 65) into the low pressure areas mentioned above. Consequently, adelayed discharge of the entire working medium, which had been receivedby means of the retarder or the connected pipelines during the brakingmode, is being supplied into the line (51) since, as a result of theshort circuit flow, a large quantity had been kept first of all in thearea of the retarder (100). This prevents a pressure impulse in the line(51). The cooling circuit area between the valve (13) and the valve (17)via the retarder (100) and the lines connected to the retarder is beingevenly drained.

A the same time, as in the previous embodiments, a damper cylinder hasbeen designed which receives working medium during the changeover frombraking mode to non-braking mode and which, in turn, removes workingmedium during the changeover from non-braking mode to braking mode. Thisshows that, in this embodiment, the line (42) carrying the workingmedium, which is connected on the opposite side of the compressionspring in the damper cylinder (30, is connected with a high-pressurearea between the check valve and the adjustable choke (43) of thecontrol valve. In the line (42), a choke (43) has been connected sothat, during the changeover from braking mode to non-braking mode, theremoved quantity of working medium could be removed in a controlled wayfrom the cooling circuit. At the same time, by means of this choke (43),the quantity of working medium of the damper cylinder (30) is suppliedinto the cooling circuit during the changeover from non-braking mode tobraking mode.

In order to achieve an optimal power loss, that is, a power loss aslittle as possible, in non-braking mode, the control valve (17) isprofitably designed in such a way that, during non-braking mode, itcompletely seals the cooling circuit of the vehicle (beginning with line51) in non-braking mode toward the conduction branch of the retarder(100). The same applies to the valve (13) which, profitably, also innon-braking mode, completely seals the cooling circuit of the vehicle(beginning with the conduction branch in which the motor (1) isdisplayed) toward the line area in which the retarder (100) is located.In addition, during non-braking mode, the valve (13) is connected insuch a way that the entire quantity of cooling fluid is directed via theline (66) into the line (51).

In order to prevent a make impulse, as indicated above, during thechangeover from braking mode to non-braking mode, the valve (13) couldbe switched into intermediate position so that initially only part ofthe cooling medium is directed via the line (67) to the retarder (100)while another part continues being directed via the line (66) toward theline (51) and, consequently, remains in the cooling circuit withouthaving to go through the retarder.

As further indicated in FIG. 4 by means of the dashed line, particularpre-determined component parts could be assembled into a water retarderunit (70).

One embodiment of this water retarder unit (70 designed in thisinvention comprises the retarder (100) and the means for adjustingpressure variations during the changeover from braking mode tonon-braking mode and vice versa. In one specific embodiment, such meansinvolve the displayed damper cylinder (30), particularly in connectionwith the choke (43), the control valve (17), and the reversing valve(13). In a particularly practical embodiment, the water retarder unit(70) also comprises the pressure relief lines (64 and 65) including theintermediary pressure shutoff valve (62). Certainly, the water retarderunit (70) has been equipped with connection points for pressure controlor pressure regulation, for instance, for pressure connection of thevalve (13) and pressure regulation of the valve (17). Also the otherlines being surrounded by the dashed line are practically integrated inthe water retarder unit (70) so that they could be connected to thecooling circuit of a motor vehicle as a flexible standard unit. For thispurpose, the water retarder unit (70), in particular, are equipped withonly one connection (71) for supplying cooling medium and only oneconnection (71) for removing cooling medium.

1. Drive unit of a vehicle with a vehicle cooling circuit, consisting ofa hydrodynamic retarder with a rotor vane wheel and a stator vane wheel,in which the hydrodynamic retarder is located in the vehicle coolingcircuit and the working medium of the retarder corresponds to thevehicle cooling medium characterized by the fact that means areconnected to the cooling circuit for the purpose of removing apre-determined quantity of working medium from the cooling circuitduring the changeover from braking mode to non-braking mode, and for thepurpose of supplying a pre-determined quantity of working medium intothe cooling circuit during the changeover from non-braking mode tobraking mode.
 2. Drive unit according to claim 1, characterized by thefact that, as a means for adjusting pressure variations, a connecteddamper cylinder is attached to the cooling circuit in such a way that,during the changeover from braking mode to non-braking mode, apre-determined quantity of working medium is removed from the coolingcircuit and, during the changeover from non-braking mode to brakingmode, a pre-determined working medium is supplied into the coolingcircuit, whereby the changeover takes place controlled andautomatically.
 3. Drive unit according to claim 2, characterized by thefact that the damper cylinder comprises a piston which is on one sideconnected pressure-conducting to the cooling circuit in front of theworkspaces of the retarder and which additionally is pressure-loaded bymeans of a compression spring in the damper cylinder and which, on theother side, is connected to the cooling circuit behind the workspace ofthe retarder via a line.
 4. Drive unit according to claim 1,characterized by the fact that a pressure relief line is connected to apressure shutoff valve at the cooling circuit and/or the retarder,whereby the pressure shutoff valve is positioned in the pressure reliefline in such a controlled way that it is opened during the changeover ofthe retarder from braking mode to non-braking mode.
 5. Drive unitaccording to claim 1, characterized by the fact that, during brakingmode, the pressure relief line is connected to the front of the retarderwith one end at a place of low pressure in flow direction and with theother end at a place of high pressure to the retarder or behind theretarder, whereby the pressure at the place of low pressure, inparticular, amounts to a maximum of 2 bar and the pressure at the placeof high pressure amounts, in particular, to between 11 and 30 bar. 6.Drive unit according to claim 1, characterized by the fact that thedrive unit has a motor and a gearbox, and that the retarder is asecondary retarder which is located in force flow direction behind thegearbox.
 7. Retarder unit, comprising a hydrodynamic retarder with arotor and a stator, whereby the hydrodynamic retarder has a vehiclecooling medium as working medium, and the retarder unit has a connectionfor the purpose of supplying cooling medium and a connection for thepurpose of removing cooling medium, characterized by the fact that theretarder unit has means for the purpose of removing a pre-determinedquantity of working medium during the changeover from braking mode tonon-braking mode, and for the purpose of supplying a pre-determinedquantity of working medium during the changeover from non-braking modeto braking mode.
 8. Retarder unit according to claim 7, characterized bythe fact that the means for the purpose of removing and supplying apre-determined quantity of working medium comprise a damper cylinderwhich has a piston which on one side is connected current-conducting tothe cooling circuit in flow direction behind the retarder via a line ata place of high pressure in the retarder unit. On its opposite side, itis connected pressure-conducting in front of the retarder via a line ata place of low pressure in the retarder unit.
 9. Retarder unit accordingto claim 7, characterized by the fact that the retarder unit also has ashutoff valve in a pressure relief line, whereby the pressure reliefline is on one end connected at a place of high pressure of the coolingcircuit in flow direction behind the retarder or at the retarder. At itsother end, the pressure relief line is connected at a place of lowpressure of the cooling circuit in flow direction in front of theretarder.
 10. Retarder unit according to claim 7, characterized by thefact that the line, at the end opposite of the damping cylinder, isconnected to a control valve, and that the retarder unit also has areversing valve in flow direction behind the connection for the purposeof supplying cooling medium and in front of the retarder which isdeveloped in such a way that in pre-determined switching positionscooling medium is directed around the retarder by means of the retarderor by means of a bypass, and that in that way the control valve, thepressure shutoff valve, and the reversing valve will be pressure-loadconnected or controlled, whereby the retarder unit has been equippedwith attached pressure-control connections.
 11. Retarder unit accordingto claim 10, characterized by the fact that the reversing valve and thecontrol valve are designed in such a way that they are completely sealedin the pre-determined switching position in which, by means of thebypass, cooling medium is being directed around the retarder in thedirection of the retarder.
 12. Drive unit according to claim 2,characterized by the fact that a pressure relief line is connected to apressure shutoff valve at the cooling circuit and/or the retarder,whereby the pressure shutoff valve is positioned in the pressure reliefline in such a controlled way that it is opened during the changeover ofthe retarder from braking mode to non-braking mode.
 13. Drive unitaccording to claim 3, characterized by the fact that a pressure reliefline is connected to a pressure shutoff valve at the cooling circuitand/or the retarder, whereby the pressure shutoff valve is positioned inthe pressure relief line in such a controlled way that it is openedduring the changeover of the retarder from braking mode to non-brakingmode.
 14. Drive unit according to claim 2, characterized by the factthat, during braking mode, the pressure relief line is connected to thefront of the retarder with one end at a place of low pressure in flowdirection and with the other end at a place of high pressure to theretarder or behind the retarder, whereby the pressure at the place oflow pressure, in particular, amounts to a maximum of 2 bar and thepressure at the place of high pressure amounts, in particular, tobetween 11 and 30 bar.
 15. Drive unit according to claim 3,characterized by the fact that, during braking mode, the pressure reliefline is connected to the front of the retarder with one end at a placeof low pressure in flow direction and with the other end at a place ofhigh pressure to the retarder or behind the retarder, whereby thepressure at the place of low pressure, in particular, amounts to amaximum of 2 bar and the pressure at the place of high pressure amounts,in particular, to between 11 and 30 bar.
 16. Drive unit according toclaim 4, characterized by the fact that, during braking mode, thepressure relief line is connected to the front of the retarder with oneend at a place of low pressure in flow direction and with the other endat a place of high pressure to the retarder or behind the retarder,whereby the pressure at the place of low pressure, in particular,amounts to a maximum of 2 bar and the pressure at the place of highpressure amounts, in particular, to between 11 and 30 bar.
 17. Driveunit according to claim 2, characterized by the fact that the drive unithas a motor and a gearbox, and that the retarder is a secondary retarderwhich is located in force flow direction behind the gearbox.
 18. Driveunit according to claim 3, characterized by the fact that the drive unithas a motor and a gearbox, and that the retarder is a secondary retarderwhich is located in force flow direction behind the gearbox.
 19. Driveunit according to claim 4, characterized by the fact that the drive unithas a motor and a gearbox, and that the retarder is a secondary retarderwhich is located in force flow direction behind the gearbox.
 20. Driveunit according to claim 5, characterized by the fact that the drive unithas a motor and a gearbox, and that the retarder is a secondary retarderwhich is located in force flow direction behind the gearbox.